Hack saw blade



y 1953 w. R. CHAPIN 2,637,355

HACK SAW BLADE Filed Nov. 22, 1950 Patented May 5, 1953 STATES PATENT OFFICE HACK SAW BLADE William R harm, In p i 1nd,, a ignon,

by mesne. ass nment to Borg-Warner Corporation, Chicago, 111;, a corporation of Illinois Application, November 22, 1950, Serial No., 197, 042

which defines a lateral wall of the. lrerf formed during operation of the blade comprises an edge of substantial lateral extent, instead oi, as in conventional practicaa sharp point, a further object of-the invention is to provide atooth shape, in a, hack saw, of suchcharac e f that. a, Summit" tial mass of metaljies. behind; an suimqr si th t. cutting edge of each tooth whichacts; to away or form the, kerf wall,

Further objects. of the-.,invent,ion will. appear as the description proceeds,

To the, accomplishment of 1 the above and r lated objects, my invention bepem od-ied in the forms illustrated in the accompanying drawings, attention being; called to the'fact, however, that the. drawings. are. illustratiye only, and,

that chang ay be made. in the pe ifi con structions illustrated and desoribeii,v SQ l ns s the scope of the appended. claims not violated Fig. 1 is a side elevation, drawn, to, a greatly enlarged scale, of two. groups ofaconventiona hachsaw teeth;

2 is aplan View thereof; Fig -3' is aview;- similar to. Fig. l butshowing znyiin-proved: blade with its novel. term of t t Fig. "1, is a-plan view thereof;-

5 is a section taken substantially on'the.

line- 5, 5'- of Fig. 1;

6; is a forwardly-facing perspective View of a single-set tooth-shaped accordance with the presentinvention; and

Fig; i is a rearwardly-iacing perspective-view of; a group of hack saw teeth embodymg the present; invention in modified form.

According to; conventional practice, a hack saw blade comprises a body l0; having teeth arrangedalon one ed e. ther i gro p f th e each ere-uh 'zom ri ine. a r ter tooth a receded by a. cu tinatooi i2; set late a y in one rec n out f the pl ne Qf. t ebo y 39 and-- a. cutting tooth 173 se l t ra lv n the pp s t d ection ut, 1 said pla e-w iarti u aflv brie e ceto Fi .24 t will. be clearthatcuttine, in h t5; of he. etteeth 1, an 1. respectively,

b i fia t: newlines-these pei ia. which. are.

stormed. the sharp some: po nts ii; andv plane of the adjacent surface of the blade body.-

almost completely unbacked, in the lineof move:

ment of the. blade during operation, areflf res quently shipped and broken, thereby destroying;

the uniformity of the effective set of the teeth. Obviously, after such chipping, the blade cannot.

run true, and smooth kerf walls. cannot,- be,

formed by the operation of the mutilated saw blade.

Very largely because of this chi ping and.

breaking, the life of a conventional hack: saw: is measured in hours, eight. cutting howls being, about average life.

Additionally, it will be. clear that uniformity of original setting of the teeth is commercially unattainable, either byknown hammer setting processes or by known push-setting processes-.-

Slight variations in the resiliency ,ofthe, teeth or in the force applied to the teeth byhammer blows, will result in slight variations in the degree-- of set attained in any: saw blade.

I have discovered that, if the outer corner; of"

the active edge of each set. tooth is; cut-, ground, honed or otherwise shaped to produce an, out;

wardly-declining cutting; edge in; place of the point M or l5, these defects in conventional haclg saw blades are effectively overcome. shaping of the tooth in this respect, to any degreei will; improve the action and life ofthe; blade; but/I presently believev that the optimum tooth shaping is attained by defining; at the outer corner of each set tooth, a surface meeting the leading face of the tooth in. an angle inclined at 145" o. th pla e f the. blade body, and at an an l of 22 /2 to the plane joining the tips of the. rakes:

teeth, that surface having one terminus in the As is clearly shown in Figs. 3, 4,, 6 and ii, the in-. clined surface, which may be plane, as shown in F 3 t 6 ?v cQnv Xly cur ed, as shown. in Fig.

'7, t p rs r arwa d y to d p a in the line joining the trailing face-and the adjacent side face of the tooth, intermediate the ends of thatline. Throughout the present: specification and claims, the word bevel and its derivatives will be used in the broadest sense to includean arrangement in which the devex surface is either plane or so curved.

My invention may be embodied in the form illus at d in Fi 3 to 6 clus ve. T ere v I have shown a fragment of a hack sawblade.

to the left of thebodv plane and, a, cutting tooth i 9 correspondingly set laterally to the right of said plane. Each raker tooth I1 is formed to provide a leading face 20, substantially perpendicular to the line of travel of the blade but, in the illustrated embodiment of the invention, leaning slightly rearwardly from the perpendicular, and an inclined trailing face or back 2| which meets the face 20 in a transversely-extending edge 22 which is perpendicular to the lateral faces 23 and 24 of the tooth ll. The faces 23 and 24 lie, respectively, in the planes of the lateral surfaces of the blade body [6.

Each tooth [8 comprises a leading face 25 sub stantially parallel with the face 23 and an inclined trailing face or back 25 meeting the face 25 in an edge 21 perpendicular to the lateral faces 28 and 29 of the tooth Hi. This tooth is set laterally with respect to the body it as is most clearly illustrated in Figs. 4 and 5. It corresponds to the tooth i2 of Figs. 1 and 2; but it differs therefrom in that an inclined surface 33 is formed thereon, thus eliminating the sharp point l of the tooth l2 and substituting therefor a cutting edge 3| of substantial lateral extent, said cutting edge being backed by a substantial mass of the metal of the tooth It. The surface 3!] tapers rearwardly to disappear, at th point 32, in the line of juncture between the surface 26 and the surface 28. As is most clearly illustrated in Fig. 5, the edge 3! inclines outwardly and toward the body [6, at an angle of 45 to the plane of the adjacent lateral surface of the body and of the surface 23 of the tooth ll, said edge having its inner terminus in that plane.

The third tooth 19 of each group comprise a leading face 33 parallel with the faces 20 and 25 and an inclined trailing face or back 34 meeting the face 33 in an edge 35; and this tooth is correspondingly set laterally in the opposite direction from the plane of the body It. The edge 35 of the tooth I9 is perpendicular to the side surfaces 36 and 3'! of that tooth; and the outwardlyprojecting corner of the tooth i9 is similarly formed with an inclined surface 38 meeting the face 33 in a cutting edge 39 inclined outwardly and toward the body It at an angle of 45 to the plane of the adjacent surface of the body it and of the side face 24 of the tooth H, the inner terminus of said edge 39 lying in said plane. The edge 39, like the edge 3!, is backed by a substantial mass of tooth metal. The surface 38 tapers rearwardly and disappears at the point 43 in the line of juncture between the surface 34 and the surface 31.

Preferably, the blade of the present invention will be manufactured by producing a conventional, set hack saw blade, and then grinding and/or honing away the corners l4 and of the set teeth to produce the surfaces 39 and 38 on each tooth I8 or i9. It will be readily apparent that, in so cutting the teeth to produce the surfaces 30 and 38, any departure from uniformity of set which may have arisen in the setting operation will be overcome, so that the edges 3i of all teeth I 8, and the edges 39 of all teeth i9 will bear a uniform relation to the blade body I6. Additionally, in thus forming the edges 31 and 39, the effects of any decarburization which may exist in the cutting portions of the set teeth, will be removed.

It will be seen, particularly by reference to Fig. 5, that kerf-wall cutting will be performed, with a blade constructed in accordance with the present invention, by th edges 3! and 39 of substantial lateral extent, effectively backed by substantial metal masses, rather than by sharp unsupported corners or points l4 and I 5 as is customary with conventional hack saw blades. As a consequence, chipping and breaking of the active portions of the set teeth is substantially completely eliminated, the life of the blade is immeasurably increased, the normality of the cut is maintained within much closer limits than has heretofore been possible with conventional blades, and the smoothness of the cutting surfaces is very greatly improved.

In the form of my invention illustrated in Fig. 7, the surface 30 of each tooth l8, and the corresponding surface of each tooth [9, will be radiused, as shown, so that the cutting edges 3| and 39' are curved lines instead of straight lines as shown in Figs. 3 to 6. Most, if not all, of the operating advantages of the form shown in Figs. 3 to 6 are retained in the form illustrated in Fig. 7, but the latter is, of course, somewhat more difiicult and expensive to produce.

While I presently believe that the objects of my invention are most perfectly accomplished in a hack saw having the tooth group arrangement herein illustrated, many of the advantages of my invention nevertheless may be attained with different tooth groupings, even those not including raker teeth, so long as the set of the teeth are provided with the beveled cutting edges herein disclosed.

I claim as my invention:

1. A hack saw having raker teeth and 0pp0- sitely set cutting teeth having leading faces and back surfaces, the back surfaces meeting at angles of generally 55' to said leading faces, the laterally-outer corners of the set teeth being bevelled to define triangular surfaces meeting said leading faces in cutting edges of substantial lateral extent, inclined at an angle of substantially 45 to the plane of the saw body, said triangular surfaces meeting said leading faces at angles of generally 78.

2. A hack saw having raker teeth and oppositely set cutting teeth, the laterally-outer corners of the set teeth being triangularly bevelled to define cutting edges of substantial lateral extent, each of said edges extending from the outermost surface of its tooth substantially into the plane of the adjacent face of the saw body.

3. A hack saw comprising a blade formed along an edge thereof with a series of teeth, each tooth having a leading face substantially perpendicu lar to said edge, and a trailing face inclined to said edge, certain of said teeth being substantially coplanar with said blade, others of said teeth being alternately set to one side or the other of the plane of said blade and having their laterally-outer corners bevelled to provide triangular surfaces forming portions of trailing faces of the set teeth, the leading and trailing faces of each set tooth meeting in a line defining the cutting edge of the set tooth and the line inclining, from the outermost surface of said tooth substantially to the plane of the adjacent face of said blade, at one angle, and, at a larger angle, to the opposite face of said tooth.

4. A hack saw comprising a planar body formed along an edge thereof with a series of teeth, each of said teeth having a leading face rooted in said edge and projecting therefrom away from said body and a back inclining from the outer end of said face rearwardly and toward said body, certain of said teeth being set laterally in one direction and others of said teeth being set laterally in the opposite direction out of the plane of said body, the back of each set tooth having a surface,

extending rearwardly from said leading face and inclined laterally outwardly and toward said body edge relative to the major portion of said back, such surface intersecting the outer lateral surface of said tooth and tapering from its intersection With said leading face to disappear short of the trailing edge of said back.

5. The hack saw of claim 4 in which each such surface is inclined at approximately 45 to the plane of said body.

6. The hack saw of claim 5 in which the inner edge of each such surface meets the leading face of its tooth substantially in the plane of the adjacent side of said body.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 938,158 Lucas Oct. 26, 1909 FOREIGN PATENTS Number Country Date 902,190 France Nov. 27, 1944 

